Mold for molding glass having a nickel and graphite surface coating

ABSTRACT

Water-soluble high molecules are made present as a dispersing agent in a dispersion coating bath of a solution of a water-soluble nickel salt containing graphite dispersed therein, and a mold for molding a glass is immersed therein in a manner that the mold serves as the cathode and the nickel metal serves as the anode in order to effect the plating while suppressing nickel or a nickel-based alloy in the film from growing in a vertical direction or in the direction of the plane thereof. On the inner surfaces of the mold is formed a film which comprises a matrix of nickel or the nickel-based alloy which as a whole has a flake-like form that is continuous and exists in an open cellular form and a graphite granule phase which is held in the open cells and is outwardly exposed on the surface. Since nickel is suppressed from growing like granules, the film exhibits excellent lubricating property, heat resistance, parting property, abrasion resistance and durability in combination, and is free from defects inherent in the prior art.

This is a Continuation of application Ser. No. 07/931,385, filed Aug.18, 1992, now abandoned.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a mold for molding a glass and to amethod of producing the same. More specifically, the invention relatesto a mold which is used for molding a parison from a molten glass (gob),and which features long life, excellent moldability and smoothness ofthe glass molded articles.

(2) Description of the Prior Art

In a step of molding a glass, masses of glass melted at a hightemperature are thrown into a mold (blank mold and neck ring). In thiscase masses of glass do not often completely flow into the mold orwrinkles develop due to frictional resistance relative to the mold. Inorder to prevent this as well as to easily remove the glass molded intothe shape of a parison from the mold, an oil (swabbing compound)containing graphite is applied onto the inner surfaces of the moldmaintaining an interval of several tens of minutes. However, since themold is usually heated at a temperature as high as about 500° C., oilsoot generates to deteriorate the working environment. Moreover, thegraphite applied in excess amounts adheres to the surfaces of the glasscontainer causing the products to be fouled and deteriorating the yieldsof the products.

In order to solve these problems, there have been proposed a variety oflubricating/parting agents to substitute for the swabbing compounds. Forinstance, Japanese Laid-Open Patent Publication No. 127111/1976discloses a lubricating/parting agent used in an apparatus for producingglass containers, comprising 5 to 30% by weight of graphite or a mixtureof graphite and a boron nitride, 5 to 30% by weight of at least onecompound selected from the group consisting of aluminum biphosphate,aluminum primary phosphate and magnesium biphosphate, and 40 to 90% byweight of an aqueous solution containing acid.

In order to impart lubricating/parting property to the inner surface ofthe mold, furthermore, Japanese Laid-Open Patent Publication No.10207/1974 discloses a mold for molding glass articles in which a nickelfilm containing phosphorus in an amount of 3 to 13% by weight isnonelectrolytically plated onto the inner surfaces of the moldmaintaining a thickness of 5 to 300 μm.

Japanese Laid-Open Patent Publication No. 100027/1980 filed by thepresent inventors discloses a mold for molding a glass wherein the innersurfaces of the mold are coated with a film in which are dispersedgraphite granules using nickel or a nickel-based alloy comprisingchiefly nickel as a matrix.

However, the former-lublicating/parting agent is yet poor in regard toheat resistance and abrasion resistance, and has a life of about 1 to 3days. The alloy coating method mentioned above is excellent in regard todurability of the film but still has a problem with respect tolubricating property which is very poor.

The latter nickel film dispersed with graphite exhibits excellentlubricating property and durability compared with those of the aboveprior art, but still tends to develop fine scars on the glass surfaces.The scars on the surface of the molded glass gradually increase afterused for extended periods of time.

That is, the film of the graphite-dispersed nickel plating exhibitsexcellent lubricating property possessed by graphite and excellent heatresistance and abrasion resistance possessed by nickel. In effecting thedispersive plating, however, the nickel layer plated on the surfaces ofthe mold greatly grow like granules in a direction perpendicularly tothe surface of the mold. Thus, scars develop in the surface of the glassbeing caused by nickel that undergo granular growth.

SUMMARY OF THE INVENTION

The object of the present invention therefore is to provide a mold formolding a glass in which nickel or a nickel-based alloy comprisingchiefly nickel serving as a matrix and graphite granules aredispersively plated on the inner surfaces of the mold for molding aglass, wherein granular growth of nickel is suppressed in order toobtain excellent lubricating property, heat resistance, partingproperty, abrasion resistance and durability in combination, eliminatingthe aforementioned defects in the prior art. The invention furtherprovides a method of producing such a mold.

According to the present invention, there is provided a mold for moldinga glass the inner surfaces of which being coated with nickel or anickel-based alloy comprising chiefly nickel and with graphite granules,wherein said coated film comprises a matrix of nickel or a nickel-basedalloy that exists in the form of open cells and a graphite granule phasethat is held in said open cells and is outwardly exposed on the surface,and said nickel or said nickel-based alloy exists in the form of thinflakes on a vertical cross section of the film in the direction of theplane thereof and in a direction perpendicular thereto in a number ofseveral percent to greater than 50 percent and having flake lengths ofnot greater than 20μm.

According-to the present invention, furthermore, there is provided amethod of producing a mold for molding a glass comprising immersing themold for molding a glass in a dispersion coating bath containing asolution of a water-soluble nickel salt with graphite being dispersedtherein in a manner that the mold serves as the cathode and the nickelmetal serves as the anode, and flowing an electric current in order toprecipitate nickel as well as graphite, wherein water-soluble highmolecules are made present as a dispersing agent in the dispersioncoating bath in order to suppress the growth of nickel or nickel-basedalloy in the film in the perpendicular direction and in the direction ofthe plane thereof. A preferred example of the water-soluble highmolecules is an anionic high molecular dispersing agent. Particularlydistinguished effects are obtained when graphite granules are used beingtreated in advance.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a electron microphotograph of the inner surface in crosssection of a metal mold for molding a glass according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, the inner surfaces of the mold arecoated with a film of nickel or a nickel-based alloy comprising chieflynickel and graphite granules by the nickel-graphite dispersion coating,The reason is because this film exhibits excellent lubricating property,heat resistance, parting property and abrasion property in combinationat the time of molding a glass.

As pointed out already, however, the film formed by the nickel-graphitedispersion coating exhibits excellent lubricating property possessed bygraphite and excellent heat resistance and abrasion resistance possessedby nickel. In effecting the dispersion coating, however, thenickel-plated layer tends to grow like granules in a directionperpendicularly to the surface of the mold or further in the directionof the plane thereof, and fine scars inevitably develop in the surfaceof the glass due to nickel that has grown like granules.

According to the present invention, it was discovered that whenwater-soluble high molecules are present as a dispersing agent in adispersive plating bath which contains a solution of a water-solublenickel salt with graphite being dispersed therein, nickel or thenickel-based alloy in the film suppressed from growing in theperpendicular direction or in the direction of the plane thereof, and afilm having a novel and fine structure is formed on the surfaces of themold for molding a glass.

The film that exists on the surface of the mold for molding a glassaccording to the present invention comprises (1) a matrix of nickel or anickel-based alloy (hereinafter simply referred to as nickel) which isof the form of thin flakes and is continuous as a whole but exists inthe form of open cells, and (2) a graphite granule phase which is heldin the open cells and is outwardly exposed on the surface. Even in thisdispersively plated film, the nickel matrix is formed through a step inwhich nickel granules precipitated by plating on the nickel granulesundergo granular growth. Therefore, the nickel matrix as a whole is in acontinuous form. In the film of the present invention, however, thenickel is suppressed from growing like granules in the perpendiculardirection or in the direction of the plane, but assumes the form of thinflakes and exists in the form of open cells, creating a distinguishedfeature. The open cell stands for a structure of a wall (cell) found ina communicating bubble-type foamed material:--though the walls arecontinuous, there necessarily exist open portions. Graphite granules areheld in the open cells consisting of nickel, and are further outwardlyexposed on the surface of the film.

The accompanying FIG. 1 is an electron microphotograph (magnification,200 times) of the cross section of the surface of the mold for molding aglass of the present invention, wherein the lower continuous portion isan underlying metal, the white thin flake-like portions in the upperfilm represent nickel-plated layer, and grey granules represent agraphite granule phase. It will be well comprehended from this drawingthat the film on the mold for molding a glass of the present inventionhas the fine structure as described above.

As will be understood from FIG. 1, the nickel-plated layer or the matrixhas the form of thin flakes of not more than 20 μm on a vertical crosssection of the film in the direction of the plane thereof and in adirection perpendicular thereto in a number of at least 50 percent ofthe entire number.

In this specification, the flake length stands for that of thenickel-plated layer that is found by taking a photograph of the crosssection of the film using a scanning electron microscope (SEM) andsubjecting it to an image processor. The magnification of the SEM imageis 700 times, and the cutting width of the image processing is 0.3 μm.

In the film on the surface of the mold for molding a glass of thepresent invention, nickel exists in the form of fine open cells andgraphite granules are held in the cells. Therefore, the film has amechanically rigid structure and exhibits excellent abrasion resistance,durability and heat resistance. Moreover, the graphite granules that areoutwardly exposed through the open cells exhibit excellent lubricatingproperty stably for extended periods of time. Moreover, since nickelexists in the form of thin flakes, molded articles of glass are notscratched even when the film is worn out; i.e., the molded articles ofglass are permitted to have smooth and excellent appearance.

In the method of the present invention, the fact was discovered as aphenomenon in that a high molecular dispersing agent blended in thedispersively plating bath suppresses the nickel from growing likegranules in a direction perpendicular to the film surface and in thedirection of the plane thereof, and brings about open cellular form andthin flake structure. Though the reason is not yet obvious, it isconsidered that the high molecular dispersing agent present in theplating bath promotes the graphite granules to adhere to the activepoints of the plated nickel that grows like granules.

Particularly great effect for suppressing the growth of granules isexhibited when an anionic high molecular dispersing agent is used as thehigh molecular dispersing agent probably due to the fact that graphitegranules precipitate on the above-mentioned active points through theanionic dispersing agent. Because of this reason, the graphite granulesare better treated in advance with the anionic high molecular dispersingagent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Mold for molding a glass)

Examples of the mold include any molds such as blank mold, finish mold,neck ring, bottom plate, baffle, press mold, etc. that are used for theproduction of bottle or jar, parisons thereof, dishes or any othermolded articles by putting a mass of molten glass or a so-called gob tosuch a molding method as press molding, blow molding, press and blowprocess or blow and blow process.

(Dispersive plating)

The film is formed on the above-mentioned mold relying upon thedispersive plating method that will be described below in detail. First,prior to effecting the dispersive plating, the inner surfaces of themold are cleansed by dewaxing with an alkali, washing with an acid,polishing with emery, or shot blasting. The mold is immersed in theplating bath in a manner that the mold serves as a cathode and nickelserves as an anode which are opposed to each other, and an electriccurrent is permitted to flow, so that graphite is precipitated togetherwith nickel to form a film. In this case, what is important is that thewater-soluble high molecular dispersing agent and, in particular, theanionic high molecular dispersing agent is made present in thedispersive plating bath.

The water-soluble high molecular dispersing agent is extensively usedfor the purpose that the granules are stably dispersed or suspended inthe aqueous medium. According to the present invention, however, theabove dispersing agent is used not only to improve the dispersion orsuspension property but also to suppress the nickel-plated layer fromgrowing like granules in a predetermined direction, which is a quitedifferent action.

Preferred examples of the water-soluble high molecular dispersing agentinclude anionic water-soluble polymers such as carboxymethyl cellulose,carboxymethyl starch, alginate, maleic acid-vinyl ether copolymer,(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylicacid-vinyl acetate copolymer, cellulose derivatives obtained bygraft-polymerizing (meth)acrylic acid or (anhydrous) maleic acid, partlyor completely saponified vinyl polyacetate, and other polymers.

Examples of the water-soluble high molecular dispersing agent mayfurther include other water-soluble high molecules such as methylcellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropylcellulose, starch, cyanoethylated starch, polyvinyl alcohol, casein,polyvinyl ether, polyethylene glycol, gum arabi, polyvinyl pyrrolidone,and the like, which may be used alone or in combination.

In the present invention, it is desired to use an anionic water-solublehigh molecular dispersing agent from the standpoint of effectivelysuppressing the granular growth of the nickel-plated layer in thedirection of height of further in the direction of the plane. Theanionic dispersing agent has anionic groups such as sulfonic acid group,phosphoric acid group or like groups. However, those dispersing agentshaving anionic groups other than carboxylic acid groups such as sulfonicacid group or phosphoric acid group, may contaminate the graphitegranules. It is therefore desired to use the dispersing agent havingcarboxylic group as anionic group. The high molecular dispersing agentmay have other hydrophilic groups such as hydroxyl group, ether group,ester group and like groups.

When expressed as a mol number per a unit weight, the concentration ofthe carboxyl groups in the water-soluble high molecular dispersing agentshould range from 100 to 1200 millimols/100 g, and particularly from 200to 1000 millimoles/100 g. When the concentration of the carboxyl groupslies outside the above-mentioned range, small effect is exhibited forsuppressing the granular growth of the nickel layer. The molecularweight of the water-soluble high molecular dispersing agent should be asgreat as what is generally regarded to be high molecules, such as 1000or greater and, particularly, 2000 or greater. The counter ions of theanionic water-soluble high molecular dispersing agent, i.e., cationsconstituting the base, may be any cations. From the standpoint ofpreventing the graphite granules from being contaminated and ofimproving the heat resistance and durability, however, the cationsshould desirably be those of an ammonium salt or an amine salt. Even incase adhered to the film, the cations of these salts easily diffuse uponheating and do not contaminate graphite granules.

Examples of amines constituting salt include alkylamines such astrimethylamine, triethylamine and n-butylamine, and alcoholamines suchas 2-dimethylamino ethanol, diethanolamine, triethnolamine,aminomethylpropanol and dimethylaminomethylpropanol. There can furtherbe used polyhydric amines such as ethylene diamine, diethylene triamine,and the like. There can further be preferably used an amine having abranched-chain alkyl group and a heterocyclic amine. Examples of theamine having branched-chain alkyl group include branched-chainalkylamines having 3 to 6 carbon atoms and, particularly, 3 to 4 carbonatoms such as isopropylamine, sec-butylamine, tert-butylamine,isoamylamine and the like. Examples of the heterocyclic amine includesaturated heterocyclic amines having a nitrogen atom such aspyrrolidene, piperidine, morpholine, and the like.

Ammonia and amines should desirably be used in amounts of at least 0.3chemical equivalent and, particularly, in amounts of from 0.7 to 1.3chemical equivalent with respect to the carboxyl groups of thewater-soluble high molecular dispersing agent.

In the film of the present invention, graphite should exist in an amountof from 5 to 70% by weight and, preferably, in an amount of 10 to 50% byweight with respect to the whole amount. When the amount of graphite issmaller than the above-mentioned range, the film loses lubricatingproperty. When the amount of graphite exceeds the above range, on theother hand, the film becomes brittle and loses abrasion resistance.

Examples of graphite include a variety of natural graphites andsynthetic graphites. Generally, however, it is desired to use a naturalgraphite having a grain size of from 0.3 to 90 μm. When the grain sizeis smaller than the above range, the granules tend to be coagulated.When the particle size is greater than the above range, on the otherhand, the film adheres less intimately to the metal and further becomesbrittle. Most preferably, the graphite should have a particle sizewithin a range of from 0.3 to 20 μm.

According to the present invention, the graphite should not be reducedby more than 50% by weight when it is exposed to the open air heated at550° C. for 24 hours, from the standpoint of maintaining lubricatingproperty of the film despite the lapse of time. Loss of graphitegranules due to oxidation is greatly affected by the presence of alkalimetals, alkaline earth metals, metal oxides or metal salts that arecontained in graphite since they work as a catalyst. The life of thefilm can be extended by using graphite granules which are highlypurified to contain ash components in amounts smaller than 100 ppm.

The matrix may be made of nickel or a nickel-based alloy comprisingchiefly nickel. An example of the nickel-based alloy may be the onewhich consists of nickel and at least one of such alloy elements as P,B, Co, Mo, Cr, W and Fe. These alloy elements may be contained inamounts of 0 to 40% by weight and, particularly, in amounts of 0.2 to30% by weight with respect to the alloy. A preferred example of thenickel-based alloy may be a nickel-phosphorus alloy in which the atomicratio of nickel to phosphorus ranges from 99.5:0.5 to 80:20 (on thebasis of weight). This nickel-phosphorus alloy exhibits particularlyexcellent abrasion resistance.

The dispersion coating bath employed in the present invention containsthe above-mentioned nickel or nickel-based alloy component, graphite andwater-soluble high molecular dispersing agent as essential components.As nickel or nickel alloy component, there can be used water-solublesalts such as of nickel or the like. As the plating bath, there can beused any known bath such as Watts bath, sulfamic acid bath or chloridebath. In this case, an Ni-P alloy-plated film can be formed ifphosphorous acid, hypophosphorous acid or salts thereof are added to theplating bath. The plating bath may, of course, be blended with a varietyof plating additives which are known per se, such as a variety ofsurfactants and, particularly, nonionic surfactants in order to improvedispersing property of the graphite.

According to the present invention, the water-soluble high moleculardispersing agent should be used in an amount of 2 to 50 parts by weightand, particularly, 5 to 30 parts by weight with respect to 100 parts byweight of graphite that is used. A representative example of the platingbath composition is described below.

    ______________________________________                                        Component     General range Preferred range                                   ______________________________________                                        Water-soluble 50 to 300 g/l 100 to 200 g/l                                    nickel salt                                                                   Phosphorous acid                                                                            0 to 40 g/l   3 to 10 g/l                                       Boric acid    0 to 80 g/l   20 to 50 g/l                                      Water-soluble 0.1 to 25 g/l 0.5 to 12 g/l                                     high molecular                                                                dispersing agent                                                              Surfactant    0 to 20 mg/l  3 to 10 mg/l                                      Graphite      5 to 50 g/l   10 to 40 g/l                                      pH            1.5 to 4      2 to 3.5                                          ______________________________________                                    

To effect the dispersion coating, the mold to be treated is immersed inthe plating bath in a manner that the mold serves as a cathode and anickel rod serves as an anode, and an electric current is permitted toflow to form a predetermined film. The current density should generallyrange from 0.5 to 10 A/dm² and, particularly, from 1 to 8 A/dm² Thevoltage for plating should be so selected as to create the above currentdensity, and generally ranges from 0.5 to 5 V.

In order that the film contains graphite in large and uniform amounts,the surface of the mold to be coated is placed on the lower side withrespect to the anode to utilize the sedimentation tendency of graphitegranules for the codeposition. In order that the interior of cavity ofthe mold is uniformly plated (codepositon), the plating operation iscarried out while shaking the mold up and down with the anode as acenter. Furthermore, the stirring operation is intermittently carriedout since the graphite granules precipitate little if the liquidcontinues to flow. It is further recommended to disperse the depositedgraphite granule layer again after every predetermined time interval,since an increase in the deposited amount of graphite granules due toprecipitation makes the formation of a dense film difficult. This isaccomplished by effecting the above stirring operation.

(Mold for molding a glass)

According to the present invention, the graphite-dispersed nickel filmplates on the inner surfaces of the mold should usually have a thicknessof from 10 to 600 μm. When the thickness is smaller than 10 μm, the filmis not desirable from the standpoint of durability. When the thicknessis greater than 600 μm, on the other hand, difficulty is involved fromthe standpoint of forming the film and an economical point of view.

According to the present invention as described above, thegraphite-dispersed nickel film plated on the inner surfaces of the mold,i.e., formed on the surfaces to which the molten glass comes in contact,comprises a matrix of nickel or a nickel-based alloy which as a wholehas a flake-like form that is continuous and exists in the form of opencells and a graphite granule phase that is held in the open cells and isoutwardly exposed on the surface.

It is essential that nickel or the nickel-based alloy exists in the formof flakes in a number of several percent to greater than 50 percent onthe vertical cross section of the film in the direction of plane thereofand in a direction perpendicular thereto, the flake length being smallerthan 20 μm. More preferably, nickel or the nickel-based alloy shouldexist in the form of granules having such a particle size that thenumber thereof is from several percent to greater than 20 percent in thedirection of the plane thereof and in a direction perpendicular thereto,the granules having a flake length of smaller than 10 μm. Moreover,nickel or the nickel-based alloy should occupy 70 to 20% of the area onthe cross section of the film.

The lubricating property due to graphite is strongly exhibited in thedirection of plane of a carbon 6-member ring (generally, in thedirection of plane of a crystal). On the film surface, therefore, thegraphite granules should be distributed in a number of several percentto greater than 50% having an angle of inclination of the graphite planeof smaller than 30 degrees from the direction of the film surface. Sucha film can be easily formed by suitably precipitating the graphite andby preventing the graphite from coagulating.

Next, working examples of the present invention will be described.

EXAMPLES Mold Example 1

A mold was dewaxed with a 1,1,1-trichloroethane, electrolyticallydewaxed in an electrolytic dewaxing solution containing 40 g of sodiumhydroxide per a liter at a temperature of 50° C. with a cathode currentdensity of 5 A/dm² for one minute, washed with water, and was thenwashed with an acid by immersing it in a 5% hydrochloric acid solutionat room temperature for 5 seconds. After further washed with water, themold was horizontally set in a plating bath having a pH of 2.5, atemperature of 65° C. and the below-described bath composition andgraphite in a manner that the inner surface (to be plated) of the moldwas faced upwards and that an anode nickel rod was located at the centerof the inner surface of the semi-cylindrical mold, and the plating waseffected with a current density of 5 A/dm² for 30 minutes. While theplating was being effected, the plating bath was stirred at a speed ofrevolution of 600 rpm for three seconds. The stirring was thendiscontinued for 15 seconds. The above operations were repeated.Furthermore, the mold was tilted by 45 degrees toward the right with theanode as a center when the stirring was effected. At the next moment ofstirring, the mold was so tilted that the inner surface thereof facedupwards and at the next moment of stirring, the mold was then tilted by45 degrees toward the left. Thus, the mold was intermittently andreciprocally turned from the rightwardly tilted angle of 45 degrees tothe leftwardly tilted angle of 45 degrees in a manner of 45 degreestoward the right, 0 degree, 45 degrees toward the left, 0 degree insynchronism with the stirring operation. Moreover, a homogenizer wasapplied to the plating bath in order to prevent graphite fromcoagulating.

    ______________________________________                                        Plating bath.                                                                 ______________________________________                                        Bath composition                                                              Hexahydrated nickel sulfate                                                                        200    g/l (118 g/l)                                     Hexahydrated nickel chloride                                                                       100    g/l (55 g/l)                                      Boric acid           40     g/l                                               Phosphorous acid     5      g/l                                               Carboxymethyl cellulose                                                                            2.5    g/l                                               SD-1 (Okuno Seiyaku Co.)                                                                           7      ml/l                                              Graphite             25     g/l                                               Graphite  Average particle size                                                                           5 μm                                                     Ash              50 ppm                                                       Iron content     30 ppm or smaller                                            Alkali metal + alkaline                                                                        10 ppm or smaller                                            earth metal                                                         ______________________________________                                         Values in parentheses represent those reckoned as anhydrates.            

Mold Example 2

The mold was dewaxed with a 1,1,1-trichloroethane, polished on itssurfaces to be plated with emery, and was set horizontally in theplating bath having the same bath composition, and graphite conditionsas those of Mold Example 1 such that the inner surface of the mold wasfaced upwards and that the anode nickel rod was located at the center ofthe inner surfaces of the semi-cylindrical mold, and was plated with acurrent density of 5 A/dm² for 30 minutes while stirring the: platingbath at a speed of revolution of 800 rpm maintaining an on-off intervalof 3 seconds on and 15 seconds off and tilting the mold in synchronismwith the stirring operation in the same manner as in Mold Example 1.Further, the homogenizer was applied prior to effecting the plating.

Mold Example 3

The plating was effected under the same conditions, i.e., samepretreatment, bath composition, graphite conditions as those of the MoldExample 1, with the exception of employing a current density of 1 A/dm²for a period of 150 minutes.

Mold Example 4

The plating was effected under the same conditions as those of MoldExample 1 but changing the stirring and mold revolution interval into a3 second-on-5 second-off cycle.

Mold Example 5

The pretreatment was carried out under the same conditions as in MoldExample 1, and the plating was effected in a plating bath having a pH of3, a temperature of 55° C. and the below-described bath composition(homogenized prior to effecting the plating) and graphite under the sameconditions (stirring, stirring and mold interval, current density andtime) as those of Mold Example 1.

    ______________________________________                                        Plating bath.                                                                 ______________________________________                                        Bath composition                                                              Hexahydrated nickel sulfate                                                                        160    g/l (94 g/l)                                      Hexahydrated nickel chloride                                                                       120    g/l (66 g/l)                                      Boric acid           40     g/l                                               Phosphorous acid     5      g/l                                               Polyvinyl alcohol    2      g/l                                               SD-1 (Okuno Seiyaku Co.)                                                                           7      ml/l                                              Graphite             30     g/l                                               Graphite  Average particle size                                                                           3 μm                                                     Ash              70 ppm                                                       Iron content     30 ppm or smaller                                            Alkali metal + alkaline                                                                        10 ppm or smaller                                            earth metal                                                         ______________________________________                                    

Mold Example 6

The pretreatment was carried out under the same conditions as in MoldExample 1, and the plating was effected under the following platingconditions by setting the mold in the plating bath having thebelow-described bath composition, conditions and graphite in the samemanner as in Mold Example 1.

    ______________________________________                                        Plating bath.                                                                 ______________________________________                                        Bath composition                                                              Hexahydrated nickel sulfate                                                                       180    g/l (106 g/l)                                      Hexahydrated nickel chloride                                                                      40     g/l (22 g/l)                                       Boric acid          40     g/l                                                Phosphorous acid    7      g/l                                                Methyl cellulose    2.5    g/l                                                SD-1 (Okuno Seiyaku Co.)                                                                          7      ml/l                                               Graphite            20     g/l                                                Bath condition.                                                                          Bath temperature 60° C.                                                Bath pH          2.5                                                          Homogenized in advance                                             Graphite   Average particle size                                                                          10 μm                                                     Ash              40 ppm                                                       Iron content     30 ppm or smaller                                            Alkali metal + alkaline                                                                        10 ppm or smaller                                            earth metal                                                        Plating condition                                                                        Stirred at 700 rpm maintaining an interval of                                 3 second-on and 10 second-off cycle.                               Mold rotated                                                                             Title intermittently toward the right and left                                by 45 degrees like in Mold Example 1, and                                     the plating was effected for 37 minutes.                           ______________________________________                                    

Comparative Mold Example 1

The plating was effected under the same pretreatment, bath compositionand graphite conditions as those of Mold Example 1 but continuouslytilting the mold by 45 degrees toward the left and right (5 rpm).

Comparative Mold Example 2

The plating was effected under the same pretreatment and graphiteconditions as those of Mold Example 1 but employing the followingplating bath composition.

    ______________________________________                                        Plating bath.                                                                 ______________________________________                                        Bath composition                                                              Hexahydrated nickel sulfate                                                                         200 g/l (118 g/l)                                       Hexahydrated nickel chloride                                                                        100 g/l (55 g/l)                                        Boric acid            40 g/l                                                  Phosphorous acid      5 g/l                                                   SD-1 (Okuno Seiyaku Co.)                                                                            7 ml/l                                                  Graphite              25 g/l                                                  Bath temperature      60° C.                                           Bath pH               2.5                                                     ______________________________________                                    

Comparative Mold Example 3

The plating was effected under the same pretreatment, plating bathcomposition and graphite conditions as those of Comparative Mold Example2, but effecting the stirring at 850 rpm and maintaining a stirring andmold rotating interval of 4 second-on and second-off cycle.

Comparative Mold Example 4

The plating was effected under the same pretreatment, plating bathcomposition and graphite conditions as those of Mold Example 5, butwithout effecting the homogenization.

Comparative Mold Example 5

The plating was effected under the same pretreatment, plating bathcomposition and plating conditions as those of Mold Example 5 but usinggraphite that is described below.

    ______________________________________                                        Graphite    Average particle size                                                                          3      μm                                                 Ash              9000   ppm                                                   containing                                                                    Fe.sub.2 O.sub.3 2600   ppm                                                   SiO.sub.2        4500   ppm                                                   Al.sub.2 O.sub.3 900    ppm                                                   CaO              400    ppm                                                   MgO              300    ppm                                                   So.sub.4         300    ppm                                       ______________________________________                                    

The results obtained are tabulated below.

                                      TABLE 1                                     __________________________________________________________________________                               Inclination                                                                         Loss (%)                                            Dispersion of Ni    angle of 30°                                                                 under                                                           Front                                                                             Inner                                                                             or smaller                                                                          550° C. ×                       Example No.                                                                          Item  As a whole                                                                          side                                                                              side                                                                              (%)   24 H  Evaluation  Dispersion level of        __________________________________________________________________________                                                       Ni                         Example                                                                              Film  50 μm                  A 1 54,000-117,000                                                                        as a                                                                                Ahole                No. 1  thickness                                                                     Ratio of                                                                            85%   85% 80%             2 65,000    inner                                                                               Aide                        smaller                                                                       than 20 μm                                                                 Number                                                                              4 μm                                                                             4 μm                                                                           5 μm                                                                           60    30    3 ⊚                                                                        graphite                                                                            good                        average                                     inclination                       flake                                                                         length                                                                        Ratio of                                                                            55%   60% 50%                         heat  good                        smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            45%   40% 50%             A 1 45,000-72,000                                                                         as a                                                                                Ahole                       Ni area                                                                Example                                                                              Film  45 μm                  2 54,000    inner                                                                               Cide                 No. 2  thickness                                                                     Ratio of                                                                            70%   75% 50%             3 ⊚ from                                                                   graphite                                                                            acceptable                  smaller                         through up  inclunation                       than 20 μm                   to about                                      Number                                                                              8 μm                                                                             6 μm                                                                           14 μm                                                                          50    30    26,000 times                                                                              heat  good                        average                         then ◯,                                                                       resistance                        flake                           then                                          length                          sproadically                                  Ratio of                                                                            40%   50% 20%             Δ.                                      smaller                                                                       than 10 μm                                                                 Ratio of                                                                            60%   55% 70%                                                           Ni area                                                                Example                                                                              Film  50 μm                  A 1 50,000-80,000                                                                         as a                                                                                Bhole                No. 3  thickness                                                                     Ratio of                                                                            65%   65% 60%             2 59,000    inner                                                                               Bide                        smaller                                                                       than 20 μm                                                                 Number                                                                              12 μm                                                                            12 μm                                                                          13 μm                                                                          60    30    3 ⊚ and                                                                    graphite                                                                            good                        average                         sporadically ◯                                                                inclination                       flake                                                                         length                                                                        Ratio of                                                                            35%   35% 35%                         heat  good                        smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            55%   55% 55%                                                           Ni area                                                                Example                                                                              Film  40 μm                  A 1 43,000-60,000                                                                         as a                                                                                Chole                No. 4  thickness                                                                     Ratio of                                                                            55%   55% 55%             2 47,000    inner                                                                               Cide                        smaller                                                                       than 20 μm                                                                 Number                                                                              18 μm                                                                            18 μm                                                                          19 μm                                                                          50    30    3 Δ   graphite                                                                            acceptable                  average                                     inclination                       flake                                                                         length                                                                        Ratio of                                                                            25%   25% 20%                         heat  good                        smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            70%   65% 75%                                                           Ni area                                                                Example                                                                              Film  50 μm                  A 1 36,000-56,000                                                                         as a                                                                                Ahole                No. 5  thickness                                                                     Ratio of                                                                            75%   75% 70%             2 45,000    inner                                                                               Aide                        smaller                                                                       than 20 μm                                                                 Number                                                                              8 μm                                                                             7 μm                                                                           9 μm                                                                           50    45    3  ⊚                                                                       graphite                                                                            acceptable                  average                                     inclination                       flake                                                                         length                                                                        Ratio of                                                                            50%   50% 45%                         heat  acceptable                  smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            55%   50% 60%                                                           Ni area                                                                Example                                                                              Film  55 μm                  A 1 54,000-68,000                                                                         as a                                                                                Bhole                No. 6  thickness                                                                     Ratio of                                                                            65%   70% 65%             2 60,000    inner                                                                               Bide                        smaller                                                                       than 20 μm                                                                 Number                                                                              10 μm                                                                            9 μm                                                                           12 μm                                                                          70    20    3 ⊚ and                                                                    graphite                                                                            good                        average                         sporadically                                                                              inclination                       flake                           ◯.                                length                                                                        Ratio of                                                                            40%   45% 35%                         heat  excellent                   smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            55%   50% 55%                                                           Ni area                                                                Comparative                                                                          Film  40 μm                  A 1 28,000-54,000                                                                         as a                                                                                Dhole                Example                                                                              thickness                                                              No. 1  Ratio of                                                                            40%   40% 40%             2 32,000    inner                                                                               Dide                        smaller                                                                       than 20 μm                                                                 Number                                                                              24 μm                                                                            23 μm                                                                          26 μm                                                                          40    30    3 X         graphite                                                                            poor                        average                                     inclination                       flake                                                                         length                                                                        Ratio of                                                                            15%   15% 15%                         heat  good                        smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            80%   80% 80%                                                           Ni area                                                                Comparative                                                                          Film  Plating is defective (normal plating is not accomplished         Example                                                                              thickness                                                                           due to local deposition of graphite).                            No. 2  Ratio of                                                                      smaller                                                                       than 20 μm                                                                 Number                                                                        average                                                                       flake                                                                         length                                                                        Ratio of                                                                      smaller                                                                       than 10 μm                                                                 Ratio of                                                                      Ni area                                                                Comparative                                                                          Film  45 μm                  A 1 34,000-63,000                                                                         as a                                                                                Dhole                Example                                                                              thickness                                                              No. 3  Ratio or                                                                            45%   50% 40%             2 50,000    inner                                                                               Dide                        smaller                                                                       than 20 μm                                                                 Number                                                                              21 μm                                                                            19 μm                                                                          26 μm                                                                          60    25    3 Δ  From first                                                                     graphite                                                                            good                        average                         to 20,000 times,                                                                          inclination                       flake                           and then X.                                   length                                                                        Ratio of                                                                            20%   25% 15%                         heat  good                        smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            60%   50% 80%                                                           Ni area                                                                Comparative                                                                          Film  55 μm                  A 1 22,000-49,000                                                                         as a                                                                                Ahole                Example                                                                              thickness                                                              No. 4  Ratio of                                                                            70%   70% 65%             2 29,000    inner                                                                               Bide                        smaller                                                                       than 20 μm                                                                 Number                                                                              9 μm                                                                             8 μm                                                                           11 μm                                                                          40    45    3 ⊚ and                                                                    graphite                                                                            poor                        average                         sporadically                                                                              inclination                       flake                           ◯.                                length                                                                        Ratio of                                                                            45%   45% 40%                         heat  acceptable                  smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            50%   40% 65%                                                           Ni area                                                                Comparative                                                                          Film  50 μm                  A 1 24,000-54,000                                                                         as a                                                                                Ahole                Example                                                                              thickness                                                              No. 5  Ratio of                                                                            75%   75% 70%             2 27,000    inner                                                                               Aide                        smaller                                                                       than 20 μm                                                                 Number                                                                              8 μm                                                                             7 μm                                                                           9 μm                                                                           60    55    3 ⊚                                                                        graphite                                                                            good                        average                                     inclination                       flake                                                                         length                                                                        Ratio of                                                                            50%   50% 45%                         heat  poor                        smaller                                     resistance                        than 10 μm                                                                 Ratio of                                                                            55%   50% 60%                                                           Ni area                                                                __________________________________________________________________________

Evaluation A: Evaluated using molds for molding 100 ml beverage bottles,

1 The number of times of molding until wrinkles and lines develop (min,number of times of molding to max, number of times of molding using 20molds).

2 Average number of times of molding.

3 Evaluation of fine scars on the bottle surfaces.

⊚ Did not at all develop.

◯ Develop to a slight degree without imposing any problem

Δ Not acceptable to those that strictly require good appearance.

× Rejected through an inspecting machine.

According to the present invention as will be obvious from the resultsof the above working examples, the water-soluble high molecules can bemade present as a dispersing agent in the dispersion coating bath of asolution of a water-soluble nickel salt in which graphite is dispersed.It is therefore allowed to suppress the growth of nickel or nickel-basedalloy in the film in the vertical direction or in the direction of theplane thereof, and to form a film of a novel fine structure comprising(1) a matrix of nickel or nickel-based alloy (hereinafter simplyreferred to as nickel) which as a whole is in a thin flake-like form andis continuous and having an open cellular form and (2) a graphitegranule phase which is held in the open cells and is outwardly exposedon the surface, on the surfaces of the mold for molding a glass. Thefilm has excellent lubricating property, heat resistance, partingproperty, abrasion resistance and durability in combination, and makesit possible to stably produce molded articles of a glass having verysmooth and excellent appearance without even fine scars for extendedperiods of time.

We claim:
 1. A mold for molding glass, the mold having inner surfaces which are coated with a film of nickel with graphite granules or with a film of a nickel-based alloy comprising chiefly nickel with graphite granules, wherein the coated film comprises:(1) a matrix of nickel or a nickel-based alloy which is in the form of flakes and is continuous as a whole in a direction perpendicular to the surface of the mold or further in a direction of the plane of said surface of the mold, but exists in the form of open cells, and (2) a graphite granule phase that is held in said open cells and is outwardly exposed on a surface of the film; wherein the matrix of nickel or the nickel-based alloy that exists in the form of open cells is suppressed from growing in the perpendicular direction or in the direction of the plane of said surface of the mold, and is present in the form of thin flakes so that the thin flakes have a grain size distribution such that at least 50 number percent of the flakes are not more than 20 μm long and that greater than 20 number percent of the flakes are smaller than 10 μm long when measured in the direction perpendicular to said surface of the mold or in the direction of the plane of said surface of the mold.
 2. A mold for molding a glass according to claim 1, wherein said nickel or said nickel-based alloy occupies 20 to 70% of an area on a cross section of the film.
 3. A mold for molding a glass according to claim 1, wherein the graphite granules are distributed in a number percent of greater than 50 having an angle of inclination of a graphite plane of smaller than 30 degrees from the surface of the film.
 4. A mold for molding a glass according to claim 1, wherein the graphite granules are highly purified to contain ash components in amounts smaller than 100 ppm.
 5. A mold for molding a glass according to claim 1, wherein the graphite has a loss of weight less than 50% when the graphite is exposed to open air heated at 550° C. for 24 hours.
 6. A mold for molding glass, the mold having inner surfaces which are coated with nickel with graphite granules or with a nickel-based alloy with graphite granules, thereby forming a film on said inner surface, wherein said film comprises:(1) a nickel or a nickel-based alloy matrix which is present in the form of thin flakes and is continuous as a whole but is present in the form of open cells; and (2) a graphite granule phase that is held in said open cells and is outwardly exposed on a surface, wherein at least 50 percent of the total number of said thin flakes are not more than 20 μm in length in a direction of the plane of the surface of said mold or in a direction perpendicular to the plane of the surface of the mold, said matrix occupying 70 to 20 percent of an area on a cross section of the film, and the graphite having a particle size of from 0.3 to 20 μm. 